Semiconductor device and semiconductor device manufacturing method

ABSTRACT

A semiconductor device includes a semiconductor substrate, a polysilicon layer fixed to the semiconductor substrate, and a silicon nitride layer in contact with the polysilicon layer, wherein the polysilicon layer includes a n-type layer and a p-type layer in contact with the n-type layer. The semiconductor device manufacturing method includes forming the polysilicon layer covering at least one hydrogen-containing layer, and heating the polysilicon layer and the hydrogen-containing layer.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-150306 filed onJul. 29, 2016 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The technology disclosed herein relates to a semiconductor device and asemiconductor device manufacturing method.

2. Description of Related Art

Japanese Patent Application Publication No. 2011-155289 (JP 2011-155289A) discloses a semiconductor device having a semiconductor substrate anda polysilicon layer formed on the semiconductor substrate. A diode (aso-called temperature detection diode) including a p-type layer and ann-type layer is formed on the polysilicon layer.

SUMMARY

The inventor(s) has found that, like JP 2011-155289 A, in the diodeinstalled on the polysilicon layer on the semiconductor substrate, manyelectrically active defects such as dangling bonds or the like arepresent on an interface with the polysilicon layer. For this reason, aleakage current is likely to flow to the diode. Accordingly, in thespecification, a technology of suppressing a leakage current of a diodeinstalled on a polysilicon layer on a semiconductor substrate isprovided.

A first aspect of the disclosure relates a semiconductor device. Thesemiconductor device includes a semiconductor substrate; a polysiliconlayer fixed to the semiconductor substrate; and a silicon nitride layerin contact with the polysilicon layer, wherein the polysilicon layerincludes a n-type layer and a p-type layer in contact with the n-typelayer.

Further, “the polysilicon layer fixed to the semiconductor substrate”may be a polysilicon layer (a polysilicon layer in contact with thesemiconductor substrate) directly formed on a surface of thesemiconductor substrate, or may be a polysilicon layer formed on asurface of another layer in a state in which the other layer (forexample, an insulating layer) is formed on the surface of thesemiconductor substrate (i.e., a polysilicon layer when another layer ispresent between the semiconductor substrate and the polysilicon layer).

In the above-mentioned semiconductor device, a diode may be constitutedby the n-type layer and the p-type layer in the polysilicon layer. Inaddition, a silicon nitride layer is disposed at a position in contactwith the polysilicon layer. During film forming of the silicon nitridelayer, a large amount of hydrogen atoms are contained in the siliconnitride layer. During film forming or after film forming of the siliconnitride layer and the polysilicon layer, the hydrogen atoms diffuse intothe polysilicon layer from the silicon nitride layer. Accordingly, thehydrogen atoms combine defects such as dangling bonds or the like(defects in the polysilicon layer) together (a so-called hydrogenterminal). Accordingly, the defects become electrically stable andhardly any leakage current flows in the diode. According to thestructure, a leakage current of the diode installed on the polysiliconlayer on the semiconductor substrate can be suppressed.

A second aspect of the disclosure relates a semiconductor devicemanufacturing method. The semiconductor device manufacturing includesforming a polysilicon layer including an n-type layer and a p-type layerin contact with the n-type layer and a hydrogen-containing layer incontact with the polysilicon layer on a semiconductor substrate; andheating the polysilicon layer and the hydrogen-containing layer.

Further, “on the semiconductor substrate” may be a position in contactwith the surface of the semiconductor substrate or may be a positionspaced apart from the surface of the semiconductor substrate. That is,the polysilicon layer or the hydrogen-containing layer may be formed ata position in contact with the surface of the semiconductor substrate,or may be formed at a position spaced apart from the surface of thesemiconductor substrate (a position with another layer interposedtherebetween). In addition, “the hydrogen-containing layer” may be asilicon nitride layer or may be a layer containing hydrogen other than asilicon nitride layer.

In a second process, hydrogen atoms are detached from thehydrogen-containing layer by heating, and the hydrogen atoms diffuseinto the polysilicon layer. Accordingly, the hydrogen atoms combinedefects such as dangling bonds or the like (defects in the polysiliconlayer), and the defects become electrically stable. As a result, hardlyany leakage current flows in the diode of the polysilicon layer (thediode constituted by the n-type layer and the p-type layer in thepolysilicon layer).

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a plan view of a semiconductor device according to anembodiment;

FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1;

FIG. 3 is a view for describing a semiconductor device manufacturingmethod according to an embodiment, showing a cross-sectional view of thesemiconductor device when an insulating film is formed on asemiconductor substrate;

FIG. 4 is a view for describing the semiconductor device manufacturingmethod according to the embodiment, showing a cross-sectional view ofthe semiconductor device when a polysilicon layer is formed on thesemiconductor substrate;

FIG. 5 is a view for describing the semiconductor device manufacturingmethod according to the embodiment, showing a cross-sectional view ofthe semiconductor device when a silicon nitride layer is formed on thesemiconductor substrate;

FIG. 6 is a view for describing the semiconductor device manufacturingmethod according to the embodiment, showing a cross-sectional view ofthe semiconductor device when a polysilicon layer is formed on thesemiconductor substrate;

FIG. 7 is a view for describing the semiconductor device manufacturingmethod according to the embodiment, showing a cross-sectional view ofthe semiconductor device when an interlayer film is formed on thesemiconductor substrate;

FIG. 8 is a view for describing the semiconductor device manufacturingmethod according to the embodiment, showing a cross-sectional view ofthe semiconductor device when a cathode electrode and an anode electrodeare formed on the semiconductor substrate;

FIG. 9 is a cross-sectional view of a semiconductor device of a variantcorresponding to FIG. 2;

FIG. 10 is a cross-sectional view of a semiconductor device of a variantcorresponding to FIG. 2; and

FIG. 11 is a cross-sectional view of a semiconductor device of a variantcorresponding to FIG. 2.

DETAILED DESCRIPTION OF EMBODIMENTS

As shown in FIG. 1, a semiconductor device 1 according to an embodimentincludes a semiconductor substrate 10, a surface electrode 12, a backsurface electrode (not shown) and a diode 50. The semiconductorsubstrate 10 is formed of, for example, silicon (Si), silicon carbide(SiC), or the like. An insulated gate bipolar transistor (IGBT), a metaloxide semiconductor field effect transistor (MOSFET), a diode, or thelike, serving as a semiconductor element is formed on the semiconductorsubstrate 10. When the semiconductor element is, for example, the IGBT,an emitter region, a collector region, a body region, a drift region,and so on, are formed on the semiconductor substrate 10. The surfaceelectrode 12 is installed on a surface of the semiconductor substrate10. While not shown, a back surface electrode is installed on a backsurface of the semiconductor substrate 10. When the semiconductorelement installed on the semiconductor substrate 10 is turned on,current flows between the surface electrode 12 and the back surfaceelectrode. The semiconductor element generates heat during an operationthereof.

The diode 50 is disposed on the semiconductor substrate 10. The diode 50is disposed on a central section of the surface of the semiconductorsubstrate 10. As shown in FIG. 2, the surface electrode 12 is notinstalled in a portion in which the diode 50 is present (i.e., thecentral section of the semiconductor substrate 10). An insulating film55 is disposed on the semiconductor substrate 10 in the portion. Theinsulating film 55 is formed of, for example, silicon oxide (SiO₂).

A polysilicon layer 150 is disposed on the insulating film 55. Thepolysilicon layer 150 includes an n-type layer 51 and a p-type layer 52.The p-type layer 52 comes in contact with the n-type layer 51. The diode50 is constituted by the n-type layer 51 and the p-type layer 52.

A plurality of silicon nitride layers 58 are disposed in the n-typelayer 51. Similarly, a plurality of silicon nitride layers 58 aredisposed also in the p-type layer 52. The entire peripheries of thesilicon nitride layers 58 are covered by the polysilicon layer 150. Thesilicon nitride layers 58 are formed of, for example, semi-insulatingsilicon nitride (SInSiN) or p-type SiN.

An interlayer film 56 is formed on the surface of the polysilicon layer150. The interlayer film 56 is insulating. The interlayer film 56 isformed of, for example, silicon oxide (SiO₂). The interlayer film 56 hastwo opening sections 156 and 157. The opening section 156 is disposed onthe n-type layer 51 and the opening section 157 is disposed on thep-type layer 52.

A cathode electrode 53 is disposed to come in contact with the n-typelayer 51 in the opening section 156. The cathode electrode 53 includes abarrier layer 53 a in contact with a surface of the n-type layer 51 andan electrode layer 53 b disposed on the barrier layer 53 a. The barrierlayer 53 a is formed of, for example, titanium (Ti). The electrode layer53 b is formed of, for example, aluminum alloy (AlSi).

An anode electrode 54 is disposed to come in contact with the p-typelayer 52 in the opening section 157. The anode electrode 54 includes abarrier layer 54 a in contact with the surface of the p-type layer 52and an electrode layer 54 b in contact with the surface of the barrierlayer 54 a. The barrier layer 54 a is formed of, for example, titanium(Ti). The electrode layer 54 b is formed of, for example, aluminum alloy(AlSi).

A protective film 57 is disposed to cover the cathode electrode 53, theanode electrode 54 and the interlayer film 56. The protective film 57 isinsulating. The protective film 57 is formed of, for example, polyimide.

Next, a method of manufacturing the semiconductor device 1 will bedescribed. Further, since the manufacturing method is characterized byformation of the diode 50, processes related to formation of the diode50 will be described below, and description of the other processes willbe omitted.

First, as shown in FIG. 3, a silicon oxide (SiO₂) layer is deposited onthe semiconductor substrate 10, and then, the insulating film 55 isformed by patterning the silicon oxide layer.

Next, the polysilicon layer 150 and the silicon nitride layers 58 areformed on the insulating film 55. The polysilicon layer 150 and thesilicon nitride layers 58 are formed as described below. First, as shownin FIG. 4, a lower layer 150 a formed of polysilicon is formed on theinsulating film 55. Next, phosphorous (P) or arsenic (As) is injected toa portion (a left portion of FIG. 3) of the lower layer 150 a to formthe n-type layer 51 a. Next, boron (B) is injected to a portion (a rightportion of FIG. 3) of the lower layer 150 a to form the p-type layer 52a. Next, as shown in FIG. 5, the silicon nitride layers 58 are formed onthe lower layer 150 a, and then, the silicon nitride layers 58 arepatterned. The silicon nitride layers 58 are formed through a methodsuch as a plasma CVD method or the like using silane (SiH₄) and ammonia(NH₃) or silane and nitrogen (N₂) as source materials. When the siliconnitride layers 58 are formed, hydrogen is introduced into the siliconnitride layers 58. For this reason, a hydrogen content in the siliconnitride layers 58 is increased. Next, as shown in FIG. 6, an upper layer150 b formed of polysilicon is formed on the silicon nitride layers 58.Next, phosphorous (P) or arsenic (As) is injected to a portion (a leftportion of FIG. 6) of the upper layer 150 b to form the n-type layer 51b. Next, boron (B) is injected to a portion (a right portion of FIG. 6)of the upper layer 150 b to form the p-type layer 52 b. Theabove-mentioned polysilicon layer 150 is constituted by the upper layer150 b and the lower layer 150 a. In addition, the above-mentioned n-typelayer 51 is constituted by the n-type layer 51 b of the upper layer 150b and the n-type layer 51 a of the lower layer 150 a. In addition, theabove-mentioned p-type layer 52 is constituted by the p-type layer 52 bof the upper layer 150 b and the p-type layer 52 a of the lower layer150 a. The polysilicon layer 150 in which the silicon nitride layers 58are disposed is completed by the above-mentioned processes.

Next, as shown in FIG. 7, the interlayer film 56 is formed by depositingsilicon oxide (SiO₂) on the polysilicon layer 150. Next, the openingsections 156 and 157 are formed in the interlayer film 56. After that,as shown in FIG. 8, the barrier layers 53 a and 54 a are formed on thesurface of the polysilicon layer 150 in the opening sections 156 and 157by forming a film using titanium (Ti) through a sputtering method or thelike. Further, the electrode layers 53 b and 54 b are formed on thebarrier layers 53 a and 54 a by forming a film using aluminum alloy(AlSi) through a sputtering method or the like. In this step, manyelectrically active crystalline defects such as dangling bonds or thelike are present in an interface of the polysilicon layer 150 (i.e., aninterface between the polysilicon layer 150 and the other layers (theinterlayer film 56, the barrier layers 53 a and 54 a, the insulatingfilm 55, and so on) and a surface (a side surface) to which thepolysilicon layer 150 is exposed).

Next, the semiconductor substrate 10 is heated. Then, hydrogen atoms aredetached from the silicon nitride layers 58. The hydrogen atoms detachedfrom the silicon nitride layers 58 diffuse into the polysilicon layer150. Accordingly, the hydrogen atoms combine defects (defects in thepolysilicon layer 150) such as dangling bonds or the like that arepresent in the polysilicon layer 150 together. Accordingly, the defectsare electrically stabilized. That is, the interface of the polysiliconlayer 150 is terminated by the hydrogen atoms.

Next, the protective film 57 is formed by forming and patterning apolyimide film. Accordingly, a structure of the diode 50 shown in FIG. 2is obtained.

Next, an operation of the semiconductor device 1 will be described. Whenthe semiconductor element in the semiconductor substrate 10 is operated,the semiconductor substrate 10 heats to a high temperature. The diode 50is used as a temperature detection diode configured to measure atemperature of the semiconductor substrate 10. A forward current havinga constant value flows in the diode 50. When a temperature of the diode50 varies according to a variation in temperature of the semiconductorsubstrate 10, a forward voltage drop of the diode 50 varies.Accordingly, the temperature of the semiconductor substrate 10 can bemeasured by measuring the forward voltage drop of the diode 50. Sincethe interface of the polysilicon layer 150 is terminated by thehydrogen, a leakage current cannot easily occur in the diode 50. Forthis reason, the current the flows to a p-n junction of the diode 50 canbe precisely controlled, and correlation between the forward voltagedrop and the temperature of the diode 50 is further stabilized.Accordingly, according to the diode 50, the temperature of thesemiconductor substrate 10 can be more accurately measured.

Further, while the configuration in which the silicon nitride layers 58are disposed in the polysilicon layer 150 has been described in theabove-mentioned embodiment, the silicon nitride layers 58 may bedisposed at other positions adjacent to the polysilicon layer 150. Forexample, as shown in FIG. 9, the silicon nitride layers 58 may bedisposed between the polysilicon layer 150 and the interlayer film 56.Alternatively, as shown in FIG. 10, the silicon nitride layers 58 may bedisposed between the insulating film 55 and the polysilicon layer 150.In addition, as shown in FIG. 11, dispositions of the silicon nitridelayers 58 in FIGS. 2, 9 and 10 may be combined. In addition, theinsulating film 55 and the interlayer film 56 (i.e., silicon oxide) caneasily contain moisture during film forming. For this reason, when thesilicon oxide film and the polysilicon layer 150 are adjacent to eachother, the leakage current can easily flow to the interface thereof dueto an influence of the moisture. As shown in FIGS. 9 to 11, when thesilicon nitride layers 58 are disposed between the silicon oxide filmand the polysilicon layer 150, entry of the moisture into thepolysilicon layer 150 can be prevented, and further, the leakage currentcan be suppressed.

In addition, in the above-mentioned embodiment, hydrogen atoms aredetached from the silicon nitride layers 58 by heating the semiconductorsubstrate 10. However, when the electrode such as the cathode electrode53, the anode electrode 54, or the like, is formed by film forming, bothof a film forming process and a heating process may be performed incombination by heating the semiconductor substrate 10.

In addition, in the above-mentioned example, while the silicon nitridelayers 58 are used as a layer for supplying hydrogen to the polysiliconlayer 150 in the manufacturing process, another layer containinghydrogen may be used. A layer having a hydrogen content larger than thatof the polysilicon layer 150 may be used during film forming.

The technical components disclosed herein will be listed below. Further,each of the following technical components is independently useful.

In the configuration of the example disclosed herein, the n-type layerand the p-type layer of the polysilicon layer function as a temperaturedetection diode configured to detect a temperature of the semiconductorsubstrate.

According to the above-mentioned configuration, since the leakagecurrent of the temperature detection diode installed on the polysiliconlayer is suppressed, the temperature of the semiconductor substrate canbe more accurately detected.

Hereinabove, while the embodiment has been described in detail, this ismerely exemplarily provided and not limited to the scope of the claims.Various modifications and variations of the above-exemplified specificexamples are included in the technology disclosed in the claims.Technical components described in the specification or the drawingsexhibit technical usefulness solely or in various combinations but arenot limited to the combinations of the claims at the time theapplication was filed. In addition, the technology disclosed in thespecification or the drawings can achieve a plurality purposes at thesame time and has technical usefulness by itself by achieving one of thepurposes.

What is claimed is:
 1. A semiconductor device manufacturing methodcomprising: providing a semiconductor substrate; forming a polysiliconlayer covering at least one hydrogen-containing layer, and including ann-type layer and a p-type layer in contact with the n-type layer,comprising: forming a first portion of the polysilicon layer over thesemiconductor substrate, wherein the first portion of the polysiliconlayer includes a first portion of the n-type layer and a first portionof the p-type layer in contact with the first portion of the n-typelayer; forming the at least one hydrogen-containing layer on at least aportion of the first portion of the n-type layer and on at least aportion of the first portion of the p-type layer; and forming a secondportion of the polysilicon layer on the at least one hydrogen-containinglayer and on at least a portion of the first portion of the polysiliconlayer, wherein: the second portion of the polysilicon layer includes asecond portion of the n-type layer and a second portion of the p-typelayer in contact with the second portion of the n-type layer, and the atleast one hydrogen-containing layer is present in the n-type layer andthe p-type layer; and heating the polysilicon layer and the at least onehydrogen-containing layer.
 2. The semiconductor device manufacturingmethod according to claim 1, further comprising forming a an additionalhydrogen-containing layer over the semiconductor substrate, before theformation of the polysilicon layer covering the at least onehydrogen-containing layer.